Fabrication of logic devices and power devices on the same substrate

ABSTRACT

A method of forming a logic device and a power device on a substrate is provided. The method includes forming a first vertical fin on a first region of the substrate and a second vertical fin on a second region of the substrate, wherein an isolation region separates the first region from the second region, forming a dielectric under-layer segment on the second vertical fin on the second region, and forming a first gate structure on the dielectric under-layer segment and second vertical fin on the second region.

BACKGROUND Technical Field

The present invention generally relates to forming a logic transistorand a power transistor on the same substrate, and more particularly tofabricating a logic transistor and a power transistor from the same setof vertical fins formed on the same region of a substrate.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the device channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the FinFET can be an upright slab of thin rectangularsilicon (Si), commonly referred to as the fin with a gate on the fin, ascompared to a MOSFET with a single gate parallel with the plane of thesubstrate. Depending on the doping of the source and drain, an n-FET ora p-FET can be formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also can be coupled to form a complementary metaloxide semiconductor (CMOS) device, where a p-channel MOSFET andn-channel MOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts becomes more difficult. An approachis therefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

In accordance with an embodiment of the present invention, a method offorming a logic device and a power device on a substrate is provided.The method includes forming a first vertical fin on a first region ofthe substrate and a second vertical fin on a second region of thesubstrate, wherein an isolation region separates the first region fromthe second region. The method further includes forming a dielectricunder-layer segment on the second vertical fin on the second region. Themethod further includes forming a first gate structure on the dielectricunder-layer segment and second vertical fin on the second region.

In accordance with another embodiment of the present invention, a methodof forming a logic device and a power device on a substrate is provided.The method includes forming a first vertical fin on a first region ofthe substrate and a second vertical fin on a second region of thesubstrate, wherein an isolation region separates the first region fromthe second region. The method further includes forming a dielectricunder-layer on the first vertical fin and the second vertical fin. Themethod further includes forming a masking block on the dielectricunder-layer and second vertical fin on the second region that leaves aportion of the dielectric under-layer on the first vertical fin exposed.The method further includes removing the exposed portion of thedielectric under-layer to form a dielectric under-layer segment on thesecond vertical fin. The method further includes removing the maskingblock, and forming a gate dielectric layer on the dielectric under-layersegment and first vertical fin on the first region.

In accordance with yet another embodiment of the present invention, alogic device and a power device on a substrate is provided. The devicesinclude a first vertical fin on a first region of the substrate and asecond vertical fin on a second region of the substrate, wherein anisolation region separates the first region from the second region. Thedevices further include a first doped well and a bottom source/drainregion in the substrate below the first vertical fin. The devicesfurther include a second doped well in the substrate below the secondvertical fin. The devices further include a bottom spacer layer on thebottom source/drain region and the second doped well. The devicesfurther include a dielectric under-layer segment on the bottom spacerlayer and the second vertical fin, and a first gate dielectric layer onthe dielectric under-layer segment.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional side view showing a substrate, in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional side view showing a plurality of verticalfins formed on the substrate with a fin template on each of the verticalfins, in accordance with an embodiment of the present invention;

FIG. 3 is a cross-sectional side view showing an isolation regionbetween two vertical fins, an n-type well below one of the verticalfins, and a p-type well below the other vertical fin, in accordance withan embodiment of the present invention;

FIG. 4 is a cross-sectional side view showing a masking block coveringone of the vertical fins and the n-type well, in accordance with anembodiment of the present invention;

FIG. 5 is a cross-sectional side view showing a liner layer on thesidewalls of the exposed vertical fin, in accordance with an embodimentof the present invention;

FIG. 6 is a cross-sectional side view showing a source/drain regionformed in the p-type well, in accordance with an embodiment of thepresent invention;

FIG. 7 is a cross-sectional side view showing the exposed vertical finsafter removing the masking block and the liner layer, in accordance withan embodiment of the present invention;

FIG. 8 is a cross-sectional side view showing a bottom spacer layer onthe source/drain region, isolation region, and n-type well, and spacercaps on the fin templates, in accordance with an embodiment of thepresent invention;

FIG. 9 is a cross-sectional side view showing a dielectric under-layeron the vertical fins, spacer caps, and bottom spacer layer, inaccordance with an embodiment of the present invention;

FIG. 10 is a cross-sectional side view showing a second masking block onthe vertical fin on the n-type well, in accordance with an embodiment ofthe present invention;

FIG. 11 is a cross-sectional side view showing the exposed vertical finon the bottom source/drain region after removing the exposed portion ofthe dielectric under-layer, in accordance with an embodiment of thepresent invention;

FIG. 12 is a cross-sectional side view showing a gate dielectric layerformed on the exposed vertical fin and the exposed dielectricunder-layer segment after removing the second masking block, inaccordance with an embodiment of the present invention;

FIG. 13 is a cross-sectional side view showing a work function layer onthe gate dielectric layer, in accordance with an embodiment of thepresent invention;

FIG. 14 is a cross-sectional side view showing a conductive gate fill onthe work function layer, in accordance with an embodiment of the presentinvention;

FIG. 15 is a cross-sectional side view showing the gate dielectriclayer, work function layer, and conductive gate fill with reducedheights, in accordance with an embodiment of the present invention;

FIG. 16 is a cross-sectional side view showing a top spacer layer formedon the conductive gate fill, work function, layer, and gate dielectriclayer, and a second set of spacer caps on the first spacer caps, inaccordance with an embodiment of the present invention;

FIG. 17 is a cross-sectional side view showing top spacers on patternedgate structures formed from the gate dielectric layer, work functionlayer, and conductive gate fill, in accordance with an embodiment of thepresent invention;

FIG. 18 is a cross-sectional side view showing a barrier layer on thegate structures and bottom spacer layer, in accordance with anembodiment of the present invention;

FIG. 19 is a cross-sectional side view showing a top source/drain formedon each of the vertical fins, in accordance with an embodiment of thepresent invention; and

FIG. 20 is a cross-sectional side view showing electrical contactsformed to each of the top source/drains, the bottom source/drain, andthe n-type doped well, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

Embodiments of the present invention relate generally to forming acombination of logic devices and power devices on a substrate from thesame set of vertical fins. A plurality of vertical fins can be formed onthe substrate and a subset of the vertical fins can be masked off todifferentiate subsequently fabricated power devices from logic devices,where power devices can handle greater voltages and power than the logicdevices.

Embodiments of the present invention relate generally to fabricating finfield effect transistors (FinFET) devices which can handle highvoltage/power using process steps similar to those used to fabricateFinFET devices which can be low voltage/power devices, so a combinationof high voltage/power devices and low voltage/power logic devices can befabricated together and at the same time on the same substrate.

Embodiments of the present invention relate generally to forming powerdevices having an additional thick dielectric under-layer and aninverted T-shaped gate structure to increase the voltage/currentcapacity of the devices. The power devices can be vertical transport finfield effect transistors (VT FinFETs) having an additional thickdielectric under-layer as part of the electrically insulating componentof a gate structure.

Embodiments of the present invention relate generally to forming powerdevices having an inverted T-shaped conductive region from a topsource/drain, through a vertical fin channel, to a lightly doped well,and a 90 degree turn to a bottom electrical contact. A single verticalfin can be formed directly on the doped well for a power FinFET. Theinverted T-shaped conductive region can control the ‘ON’ resistance ofthe power device, so it can handle greater voltages/power than a devicewithout the inverted T-shaped conductive region. The well depth, dopantconcentration, and distance from the channel to the bottom electricalcontact can affect the device resistance and operating voltage range. Ahigher doped source/drain region may not be used in the power device.

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: circuitry and devices involvinga combination of power devices and control circuitry on the samesubstrate, for example, System-on-Chip (SoC) devices.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a substrate is shown, inaccordance with an embodiment of the present invention

In one or more embodiments, a substrate 110 can be, for example, asingle crystal semiconductor material wafer or asemiconductor-on-insulator stacked wafer. The substrate can include asupport layer that provides structural support, and an activesemiconductor layer that can form devices. An insulating layer (e.g., aburied oxide (BOX) layer) may be between the active semiconductor layerand the support layer to form a semiconductor-on-insulator substrate(SeOI) (e.g., a silicon-on-insulator substrate (SOI)), or an implantedlayer can form a buried insulating material.

The support layer can include crystalline, semi-crystalline,micro-crystalline, nano-crystalline, and/or amorphous phases. Thesupport layer can be a semiconductor (e.g., silicon (Si), siliconcarbide (SiC), silicon-germanium (SiGe), germanium (Ge),gallium-arsenide (GaAs), cadmium-telluride (CdTe), etc.), an insulator(e.g.: glass (e.g. silica, borosilicate glass), ceramic (e.g., aluminumoxide (Al₂O₃, sapphire), plastic (e.g., polycarbonate,polyacetonitrile), metal (e.g. aluminum, gold, titanium,molybdenum-copper (MoCu) composites, etc.), or combination thereof.

The active semiconductor layer can be a crystalline semiconductor, forexample, a IV or IV-IV semiconductor (e.g., silicon (Si), siliconcarbide (SiC), silicon-germanium (SiGe), germanium (Ge)), a III-Vsemiconductor (e.g., gallium-arsenide (GaAs), indium-phosphide (InP),indium-antimonide (InSb)), a II-VI semiconductor (e.g.,cadmium-telluride (CdTe), zinc-telluride (ZnTe), zinc sulfide (ZnS),zinc selenide (ZnSe)), or a IV-VI semiconductor (e.g., tin sulfide(SnS), lead selenide (PbSb)).

FIG. 2 is a cross-sectional side view showing a plurality of verticalfins formed on the substrate with a fin template on each of the verticalfins, in accordance with an embodiment of the present invention.

In one or more embodiments, a plurality of vertical fins 111 can beformed on the substrate 110, where the vertical fins can be formed by amultiple patterning fabrication process, for example, a sidewall imagetransfer (SIT) process, a self-aligned double patterning (SADP) process,self-aligned triple patterning (SATP) process, or a self-alignedquadruple patterning (SAQP). The vertical fins may be formed by a directwrite process or double patterning process using, for example, immersionlithography, extreme ultraviolet lithography, or x-ray lithographyfollowed by etching.

In various embodiments, the vertical fins can have a height in the rangeof about 15 nm to about 100 nm, or about 15 nm to about 50 nm, or about50 nm to about 100 nm, or about 30 nm to about 70 nm, although otherheights are contemplated.

In various embodiments, a fin template 120 may be on each vertical fin111, where the fin template 120 is formed during the patterning process.The fin templates 120 can be a hardmask, for example, silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a silicon boro carbonitride (SiBCN), a boron carbide (BC), aboron nitride (BN), or combinations thereof. A thin (i.e., <1 nm) oxidelayer can be between the top surface of the vertical fin 111 and the fintemplate 120.

FIG. 3 is a cross-sectional side view showing an isolation regionbetween two vertical fins, an n-type well below one of the verticalfins, and a p-type well below the other vertical fin, in accordance withan embodiment of the present invention.

In one or more embodiments, an isolation region 130 (e.g., a shallowtrench isolation (STI) region) can be formed in the substrate 110, wherethe isolation region can include an insulating dielectric material(e.g., SiO₂) to prevent or reduce electrical conduction betweendifferent regions of the substrate 110. The isolation region 130 canhave a width of at least 50 nm, or at least 100 nm or about 50 nm toabout 250 nm, or about 100 nm to about 150 nm, to physically andelectrically separate adjacent regions of the substrate. One or morevertical fins 111 can be formed on each side of the isolation region130, wherein the isolation region 130 separates the substrate into twodifferent regions, for example, a first region 101 and a second region102. One or more vertical fins 111 formed in the first region 101 can beconfigured to form a p-type logic fin field effect transistor (FinFET),and one or more vertical fins 111 formed in the second region 102 can beconfigured to form an n-type power fin field effect transistor, althoughthe arrangement and/or dopant type can be reversed.

In one or more embodiments, dopants can be introduced into the substrate110 to form doped wells 115, 116. A p-type dopant can be introduced intothe substrate 110 in the first region 101 to form a p-type doped well115, and an n-type dopant can be introduced into the substrate in thesecond region 102 to form an n-type doped well 116. In variousembodiments the dopants can be reversed. P-type dopants can include, butnot be limited to, boron (B), aluminum (Al), gallium (Ga), and indium(In). N-type dopants can include, but not be limited to, phosphorus (P),arsenic (s), and antimony (Sb). Dopants (n-type or p-type) can beincorporated by suitable doping techniques, including but not limitedto, ion implantation, gas phase doping, plasma doping, plasma immersionion implantation, cluster doping, infusion doping, liquid phase doping,solid phase doping, etc. The doped wells 115, 116 can be adjacent to theisolation region 130, where the doped wells 115, 116 can be shallowerthan the isolation region 130. The doped wells 115, 116 can be below thevertical fins 111, where the doped wells extend laterally beyond theinterfacial area of the one or more vertical fins 111. The doped well116 for a power FinFET can have a depth into the substrate 110 in arange of about 30 nm to about 150 nm, or about 50 nm to about 100 nm,although other depths are also contemplated. Changing the depth of thedoped well 116 can alter the device resistance and operating voltage ofthe power device. The doped well 115 for a logic FinFET can have a depthinto the substrate 110 in a range of about 20 nm to about 100 nm, orabout 20 nm to about 60 nm, or about 50 nm to about 100 nm, althoughother depths are also contemplated.

In various embodiments, the p-type doped well 115 can have a dopantconcentration in the range of about 1×10¹⁷ atoms/cm³ to about 1×10¹⁹atoms/cm³, or about 5×10¹⁷ atoms/cm³ to about 5×10¹⁸ atoms/cm³. Invarious embodiments, the n-type doped well 116 can have a dopantconcentration in the range of about 1×10¹⁷ atoms/cm³ to about 1×10¹⁹atoms/cm³, or about 5×10¹⁷ atoms/cm³ to about 5×10¹⁸ atoms/cm³. A dopedwell 115, 116 can have a lower dopant concentration to provide forhigher voltages across the device channel. By controlling the dopantconcentrations of the p-type doped well 115 and n-type doped well 116, alogic device and a power device can be formed on the same substrate 110using essentially the same process steps. A power device can have anoperating voltage in a range of about 3 volts (V) to about 10 V, whereasa logic (i.e., low voltage) device can have an operating voltage in arange of about 0.5 V to about 2 V. In various embodiments, a lowerdopant concentration of the n-type doped well 116 can form the powerdevice(s), while the higher dopant concentration p-type doped well 115can form the logic device(s). This also provides fabricationefficiencies and greater leeway in forming electronic devices on thesame substrate (e.g., system-on-chip).

FIG. 4 is a cross-sectional side view showing a masking block coveringone of the vertical fins and the n-type well, in accordance with anembodiment of the present invention.

In one or more embodiments, a masking layer can be formed on thevertical fins 111, isolation region 130, and the substrate 110, wherethe masking layer can be formed by a blanket deposition (e.g., CVD,spin-on). The masking layer can extend above the top surface of the fintemplates 120, and a chemical mechanical polishing (CMP) used to reducethe height and provide a planarized surface. The masking layer can be asoft mask material, for example, a lithography resist material, such asa polymeric material (e.g. poly(methyl methacrylate) (PMMA), siloxanes,polydimethylsiloxane (PDMS), hydrogen silsesquioxane (HSQ), tetraethylorthosilicate (TEOS), etc.) or amorphous carbon (a-C).

In various embodiments, the masking layer can be a hard mask comprisinga dielectric material such as silicon nitride (SiN), silicon oxide(SiO), a silicon oxynitride (SiON), a silicon carbide (SiC), a siliconoxygen carbonitride (SiOCN), or a silicoboron carbonitride (SiBCN). Invarious embodiments, the masking layer is a silicon nitride. In variousembodiments, the masking layer can have a thickness of about 10 nm toabout 100 nm, or about 10 nm to about 30 nm, although other thicknessesare also contemplated. The masking layer can have a thickness of about100 nm.

In various embodiments, the masking layer can be patterned to form amasking block 140 covering the vertical fins 111 and the n-type dopedwell 116 in the second region 102 by lithographic methods. A portion ofthe masking layer can be removed to expose the vertical fins 111 andp-type doped well 115 in the first region 101. A portion of theisolation region 130 may be exposed and a portion of the isolationregion 130 may be masked. The masking block 140 can extend above the topsurface of the fin templates.

FIG. 5 is a cross-sectional side view showing a liner layer on thesidewalls of the exposed vertical fin, in accordance with an embodimentof the present invention.

In one or more embodiments, a liner layer 150 can be formed on thesidewalls and endwalls of the exposed vertical fins 111, where theexposed vertical fins 111 can be on the first region 101. The linerlayer 150 can be formed by a conformal deposition (e.g., atomic layerdeposition (ALD), plasma enhanced ALD (PEALD), chemical vapor deposition(CVD), plasma enhanced CVD (PECVD), or a combination thereof, to apredetermined thickness. In various embodiments, the liner layer 150 canhave a thickness in the range of about 3 nm to about 15 nm, or in therange of about 4 nm to about 8 nm, where the liner layer can be thickenough to prevent penetration of dopants into the vertical fins 111.

FIG. 6 is a cross-sectional side view showing a bottom source/drainregion formed in the p-type well, in accordance with an embodiment ofthe present invention.

In various embodiments, a bottom source/drain region 118 can be formedin the substrate 110, where the bottom source/drain region 118 can beformed in a p-type well 115 or an n-type well 116. Dopants (n-type orp-type) can be incorporated by suitable doping techniques, including butnot limited to, ion implantation, gas phase doping, plasma doping,plasma immersion ion implantation, cluster doping, infusion doping,liquid phase doping, solid phase doping, etc. In various embodiments,the bottom source/drain region 118 can be doped to form n-type or p-typesource/drains to fabricate NFETs or PFETs. The dopant forming the bottomsource/drain region 118 can be the opposite type as the doped well 115in the first region 101, such that the doped well 115 can form apunch-through stop layer. In various embodiments, phosphorus dopedsilicon can be used as the bottom source/drain region 118 for NFETs. Ap-type doped well and an n-type bottom source/drain region 118 can beformed in the substrate 110 below the vertical fin 111 on the firstregion 101, and an n-type doped well 116 can be formed in the substrate110 below the vertical fin 111 on the second region 102, where a bottomsource/drain region may not be formed in the doped well 116. In variousembodiments the dopants can be reversed, such that a p-type bottomsource/drain region 118 can be formed in an n-type doped well 116, and ap-type doped well can be used for a power device. In variousembodiments, a bottom source/drain region is not formed in the dopedwell for the power device. A vertical fin 111 can be directly on a dopedwell 115, 116.

In various embodiments, the bottom source/drain region 118 can have adopant concentration in the range of about 1×10¹⁸ atoms/cm³ to about1×10²¹ atoms/cm³, or about 1×10¹⁹ atoms/cm³ to about 5×10²⁰ atoms/cm³,although other concentrations are also contemplated. The dopantconcentration of the bottom source/drain region 118 can be sufficient tocounteract the opposite doping of the doped well 115. In variousembodiments, the dopant concentration of the bottom source/drain region118 can be at least 5 times (5×) the dopant concentration of the dopedwell 115 and/or doped well 116.

In various embodiments, the bottom source/drain region 118 can have adepth into the substrate 110 and doped well 115 in the range of about 20nm to about 60 nm, or about 30 nm to about 50 nm. Other depths that arelesser than, or greater than, the aforementioned depth ranges may alsobe employed. The depth into the substrate of the doped well 115 can bein the range of about 20 nm to about 60 nm, or about 50 nm to about 100nm, where the depth into the substrate of the doped well 115 is greaterthan the depth of the bottom source/drain region 118. The doped well 115can surround the bottom source/drain region 118 to form a punch-throughstop around the bottom source/drain region. The doped well 116 in thesecond region 102 may not be modified or have a bottom source/drainregion formed.

FIG. 7 is a cross-sectional side view showing the exposed vertical finsafter removing the masking block and the liner layer, in accordance withan embodiment of the present invention.

In one or more embodiments, the masking block 140 can be removed fromthe one or more vertical fins 111 on the doped well 116 in the secondregion 102. The masking block 140 can be removed using a selective etchor ashing depending on the material of the masking block. Removal of themasking block 140 can expose the vertical fins 111 and doped well 116 inthe second region 102.

FIG. 8 is a cross-sectional side view showing a bottom spacer layer onthe source/drain region, isolation region, and n-type doped well, andspacer caps on the fin templates, in accordance with an embodiment ofthe present invention.

In one or more embodiments, a bottom spacer layer 160 can be formed onthe surface of the substrate 110, the source/drain region 118, theisolation region 130, and doped well 116, as well as on a lower portionof the vertical fins in both the first and second regions 101, 102.Spacer caps 162 can be formed on the fin templates 120.

In various embodiments, the bottom spacer layer 160 can be formed by adirectional deposition, for example, a high density plasma CVD (HDPCVD),physical vapor deposition (PVD), or gas cluster ion beam (GCIB), or ablanket deposition and etch-back. In embodiments that use PVD, asputtering apparatus may include direct-current diode systems, radiofrequency sputtering, magnetron sputtering, or ionized metal plasmasputtering. In embodiments that use GCIB deposition, a high-pressure gasis allowed to expand in a vacuum, subsequently condensing into clusters.The clusters can be ionized and directed onto a surface, providing ahighly anisotropic deposition.

In various embodiments, the material of the bottom spacer layer 160 canbe a dielectric material including, but not be limited to, silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a low-K dielectric, or combinations thereof. A low-K dielectriccan include amorphous carbon (a-C), fluorine doped silicon oxide(SiO:F), carbon doped silicon oxide (SiO:C), SiCOH, silicon borocarbonitride (SiBCN), or a combination thereof. Other examples include,Applied Material's Black Diamond™.

In various embodiments, the bottom spacer layer 160 can have a thicknessin the range of about 3 nm to about 15 nm, or in the range of about 5 nmto about 10 nm, or about 3 nm to about 5 nm, although other thicknessesare contemplated.

FIG. 9 is a cross-sectional side view showing a dielectric under-layeron the vertical fins, spacer caps, and bottom spacer layer, inaccordance with an embodiment of the present invention.

In one or more embodiments, a dielectric under-layer 170 can be formedon the exposed portions of the vertical fins 111 and bottom spacer layer160, where the dielectric under-layer 170 can be formed by a conformaldeposition (e.g., ALD, PEALD).

In an embodiment dielectric under-layer 170 may be deposited usingvarious deposition techniques, for example, nitridation, atomic layerdeposition (ALD), molecular layer deposition (MLD), chemical vapordeposition (CVD), physical vapor deposition (PVD), and spin ontechniques. In an alternate embodiment the dielectric under-layer 170may be deposited using thermal oxidation as a deposition technique. Inthis alternate embodiment dielectric under-layer 170 is formed onexposed surfaces of the fin, and dielectric under-layer 170 is notformed in the inactive region which is already covered by dielectricmaterial (e.g., oxide). In an embodiment, the dielectric under-layer 170may include one or more layers. In an embodiment, dielectric under-layer170 may have a thickness in a range of about 1 nm to 25 nm, or about 2nm to 20 nm, or about 4 nm to 15 nm, or ranges there between, althoughother thicknesses are also contemplated.

In various embodiments, the dielectric under-layer 170 can have athickness in the range of about 5 nm to about 20 nm, or in the range ofabout 6 nm to about 15 nm, or in the range of about 7 nm to about 10 nm.Other thicknesses that are lesser than, or greater than, theaforementioned thickness range may also be employed.

In various embodiments, the material of the dielectric under-layer 170can be silicon oxide (SiO), silicon oxynitride (SiON), silicon borocarbonitride (SiBCN), silicon oxycarbonitride (SiOCN), a high-Kdielectric material, or combinations thereof. Examples of high-kmaterials include but are not limited to metal oxides, such as, hafniumoxide (HfO), hafnium silicon oxide (HfSiO), hafnium silicon oxynitride(HfSiON), lanthanum oxide (LaO), lanthanum aluminum oxide (LaAlO),zirconium oxide (ZrO), zirconium silicon oxide (ZrSiO), zirconiumsilicon oxynitride (ZrSiON), tantalum oxide (TaO), titanium oxide (TiO),barium strontium titanium oxide (BaSrTiO), barium titanium oxide(BaTiO), strontium titanium oxide (SrTiO), yttrium oxide (YO), aluminumoxide (AlO), lead scandium tantalum oxide (PbScTaO), and lead zincniobate (PbZnNbO). The high-k material may further include dopants suchas lanthanum, aluminum, magnesium, or combinations thereof.

FIG. 10 is a cross-sectional side view showing a second masking block onthe vertical fin on the n-type well, in accordance with an embodiment ofthe present invention.

In one or more embodiments, a second masking block 145 can be formed onthe dielectric under-layer 170 and the vertical fins 111 in the secondregion 102. A portion of the dielectric under-layer 170 can be exposedin the first region 101.

FIG. 11 is a cross-sectional side view showing the exposed vertical finon the source/drain region after removing the exposed portion of thedielectric under-layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the exposed portion of the dielectricunder-layer 170 can be removed, for example, using an isotropic etch(e.g., wet chemical etch, dry plasma etch) to form a dielectricunder-layer segment 172, and expose the underlying bottom spacer layer160, vertical fins 111, fin templates 120, and spacer caps 162. Invarious embodiments, the dielectric under-layer 170 is a differentmaterial than the bottom spacer layer 160, so portions of the dielectricunder-layer 170 can be selectively removed.

FIG. 12 is a cross-sectional side view showing a gate dielectric layerformed on the exposed vertical fin and the exposed dielectricunder-layer segment after removing the second masking block, inaccordance with an embodiment of the present invention.

In one or more embodiments, a gate dielectric layer 180 can be formed onthe exposed vertical fins 111 and the exposed dielectric under-layersegment 172 on the vertical fin in the second region 102 after removingthe second masking block 145. The gate dielectric layer 180 can beformed by a conformal deposition (e.g., ALD, PEALD).

In one or more embodiments, a gate dielectric layer 180 can be siliconoxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), boronnitride (BN), high-k dielectric materials, or a combination thereof.

In various embodiments, the gate dielectric layer 180 can have athickness in the range of about 7 Å to about 30 Å, or about 7 Å to about10 Å, or about 1 nm to about 2 nm, although other thicknesses arecontemplated.

FIG. 13 is a cross-sectional side view showing a work function layer onthe gate dielectric layer, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a work function material (WFM) can form awork function layer 190 on a portion of the gate dielectric layer 180 toform a gate structure for a fin field effect transistor (FinFET) orpower FinFET. The work function layer 190 can be deposited on the gatedielectric layer 180 by a conformal deposition. In various embodiments,the current can flow vertically from the bottom source/drain region 118or a doped well 116 through a channel region formed by the vertical fin111 and the gate structure to a top source/drain.

In various embodiments, the work function layer 190 can include, but notnecessarily be limited to, titanium nitride (TiN), tantalum nitride(TaN) or ruthenium (Ru), for a PFET. The work function layer 190 caninclude, but not necessarily be limited to, titanium nitride (TiN),titanium aluminum nitride (TiAlN), titanium aluminum carbon nitride(TiAlCN), titanium aluminum carbide (TiAlC), tantalum aluminum carbide(TaAlC), tantalum aluminum carbon nitride (TaAlCN) or lanthanum (La)doped TiN or TaN, for an NFET.

The work function layer 190 can have a thickness in the range of about 2nm to about 10 nm, or about 3 nm to about 6 nm, although otherthicknesses are contemplated.

FIG. 14 is a cross-sectional side view showing a conductive gate fill onthe work function layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a conductive gate fill 200 can be formed onat least a portion of the work function layer 190 or gate dielectriclayer 180 if the work function layer is not present. The conductive gatefill 200 can be formed by a blanket deposition, and a CMP can be used toremove excess material.

In various embodiments, the conductive gate fill 200 can include, butnot necessarily be limited to, amorphous silicon (a-Si), or metals, forexample, tungsten (W), cobalt (Co), zirconium (Zr), tantalum (Ta),titanium (Ti), aluminum (Al), ruthenium (Ru), copper (Cu), metalcarbides (e.g., TaC, TiC, WC, etc.), metal nitrides (e.g., TaN, ZrN,etc.), transition metal aluminides (e.g., TiAl, CoAl, NiAl, etc.),tantalum magnesium carbide, or combinations thereof. The conductive gatefill 200 can be deposited on the work function layer 190, or the gatedielectric layer 180 if a work function layer is not present, to formthe gate structure.

FIG. 15 is a cross-sectional side view showing the gate dielectriclayer, work function layer, and conductive gate fill with reducedheights, in accordance with an embodiment of the present invention.

In one or more embodiments, the height of the conductive gate fill 200can be reduced using, for example, a directional etch (e.g., reactiveion etch (RIE)). The exposed portion of the work function layer 190 canbe removed using a selective etch, and the exposed portion of the gatedielectric layer 180 can be removed using a selective etch to expose anupper portion of the vertical fins 111.

FIG. 16 is a cross-sectional side view showing a top spacer layer formedon the conductive gate fill, work function layer, and gate dielectriclayer, and a second set of spacer caps on the first spacer caps, inaccordance with an embodiment of the present invention.

In one or more embodiments, a top spacer layer 210 can be formed on theconductive gate fill 200, work function layer 190, and gate dielectriclayer 180, and a second set of spacer caps 212 can be formed on thefirst spacer caps 162. In various embodiments, the top spacer layer 210can be formed by a directional deposition, for example, a high densityplasma CVD (HDPCVD) or gas cluster ion beam (GCIB). The top spacer layer210 can cover the exposed upper portion of the vertical fins 111, wherethe top surface of the top spacer layer 210 can be at, above, or belowthe top surface of the vertical fins 111.

In various embodiments, the material of the top spacer layer 210 can bea dielectric material, including, but not be limited to, silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a low-K dielectric, or combinations thereof.

In another embodiments, an organic planarization layer (OPL) can beformed on the conductive gate fill 200, and patterned to expose portionof the conductive gate fill 200, which can then be removed, followed byremoval of the work function layer. A top spacer layer 210 can be formedon the remaining portions of the conductive gate fill 200.

FIG. 17 is a cross-sectional side view showing top spacers on patternedgate structures formed from the gate dielectric layer, work functionlayer, and conductive gate fill, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the top spacer layer 210, conductive gatefill 200, work function layer 190 and gate dielectric layer 180 can bemasked and etched to form a logic FinFET in the first region 101, and apower FinFET in the second region 102. The layers can be divided to forma gate structure for the power FinFET, including a first gate dielectriclayer, first work function layer, and first conductive gate fill, and agate structure for the logic FinFET, including a second gate dielectriclayer, second work function layer, and second conductive gate fill. Thegate structure of the power FinFET can have an inverted T-shape due tothe formation of the dielectric under-layer segment 172 and gatedielectric layer 180 on the bottom spacer layer 160 before removal ofportions of the top spacer layer 210, conductive gate fill 200, workfunction layer 190, gate dielectric layer 180, and dielectricunder-layer segment 172. The gate structure of the logic FinFET also canhave an inverted T-shape due to the formation of the gate dielectriclayer 180 on the bottom spacer layer 160 before removal of portions ofthe top spacer layer 210, conductive gate fill 200, work function layer190, gate dielectric layer.

A trench can be formed between a gate structure in the first region 101and a gate structure in the second region 102, where the trench can beover the isolation region 130 to physically and electrically separatethe gate structure on the first region from the gate structure on thesecond region.

FIG. 18 is a cross-sectional side view showing a barrier layer on thegate structures and bottom spacer layer, in accordance with anembodiment of the present invention.

In one or more embodiments, a barrier layer 220 can be formed on thegate structures and bottom spacer layer, where the barrier layer can beformed by a conformal deposition. The barrier layer 220 can be formedusing a conformal deposition process, for example, atomic layerdeposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD),although other suitable conformal deposition processes may be used. Thebarrier layer 220 can be made of silicon nitride (SiN), siliconcarbonitride (SiCN), silicon boron nitride (SiBN), a doped nitride,silicon oxynitride (SiON), or combinations thereof. In variousembodiments, the barrier layer 220 may be made of silicon nitride. Thebarrier layer 220 can have a uniform thickness ranging from about 3 nmto about 10 nm. The barrier layer 220 can be sufficiently thick toprevent diffusion of material from the conductive gate fill 200 into aninterlayer dielectric (ILD) layer.

FIG. 19 is a cross-sectional side view showing a top source/drain formedon each of the vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, and ILD layer 230 can be formed on thebarrier layer 220, where the ILD layer 230 can be formed by a blanketdeposition and a CMP used to exposed a portion of the barrier layer 220.The ILD layer can be a dielectric (e.g., SiO, SiO:C, etc.).

In various embodiments, an exposed portion of the barrier layer 220 canbe removed to expose the underlying second spacer caps 212. The secondspacer caps 212 and first spacer caps 162 can be selectively removed toexpose the fin template 120, and the fin template 120 can be removed toform an opening over the top surface of the vertical fins 111. Thesecond spacer caps and first spacer caps can be the same material.

In one or more embodiments, a top source/drain 240 can be formed on eachof the vertical fins 111. The top source/drain 240 can be formed byepitaxial growth on the exposed surface of the vertical fin 111.

FIG. 20 is a cross-sectional side view showing electrical contactsformed to each of the top source/drains, the bottom source/drain, andthe n-type doped well, in accordance with an embodiment of the presentinvention.

In one or more embodiments, vias or trenches can be formed in the ILDlayer 230 down to the bottom source/drain region 118, doped well 116,and the top source/drains 240. Via and trench liner layers can be formedin the vias and trenches to act as diffusion barriers, and can form ametal silicide (e.g., TiSi) on the bottom source/drain region 118, dopedwell 116, and the top source/drains 240. The via liner layers can be atitanium (Ti) and titanium nitride (TiN) bilayer.

Contact layers 250 can be formed on the bottom source/drain region 118,doped well 116, and the top source/drains 240 to improve electricalconnectivity and reduce resistance. The contact layers 250 can be formedby epitaxial growth of silicon (Si) and/or silicon-germanium (SiGe) onthe bottom source/drain region 118, doped well 116, and the topsource/drains 240, where the contact layers 250 can be highly doped.Doping of the contact layers 250 can be performed using, for example,ion implantation, or annealing, or in situ during an epitaxial process.In a non-limiting illustrative example, the doping of the contact layer250 uses, for example, arsenic (As) or phosphorous (P) for n-type device(e.g., nFET), and boron (B) for a p-type device (e.g., pFET), atconcentrations in the range of about 1×10²⁰ atoms/cm³ to about 1×10²¹atoms/cm³. In various embodiments, the dopant concentration of thecontact layers 250 can be at least 5 times the dopant concentration ofthe doped wells 115, 116, or similar to the bottom source/drain 118.

In various embodiments, top electrical contacts 270 can be formed on thecontact layers 250 on the top source/drains 240, and bottom electricalcontacts 260 can be formed on the contact layers 250 on the bottomsource/drain region 118 and the doped well 116. The bottom electricalcontacts 260 and top electrical contacts 270 can be a conductivematerial, for example, tungsten (W), tantalum (Ta), tantalum nitride(TaN), cobalt (Co), ruthenium (Ru), or any other conductor that can beconformally deposited. These bottom electrical contacts 260 and topelectrical contacts 270 can be deposited in blanket form (covering allexposed surfaces) and then polished, using for example, chemicalmechanical polishing (CMP). A gate contact can be formed to each gate.

In various embodiments, the bottom electrical contact 260 and contactlayer 250 can be separated by a lateral distance, D₁, from the dopedwell 116 in a range of about 20 nm to about 200 nm, or in a range ofabout 50 nm to about 100 nm, although other distances are alsocontemplated, where the lateral distance, D₁, can alter the resistanceand voltage capacity of the power device.

In various embodiments, the n-type doped well 116 or p-type doped well115 and bottom source/drain region 118 through a vertical fin to the topsource/drain 240 can form an inverted T-shaped conductive region 119between the bottom electrical contacts 260 and top electrical contacts270. The inverted-T shape well can achieve an optimal tradeoff betweenthe device's ON-resistance and high voltage capability. The depth of thewell 116 can provide another variable for tuning the well resistancewithout increasing the footprint (i.e., area) of the power transistor.This inverted T-shaped conductive region can allow the power transistorto handle a much higher power. The inverted T-shaped conductive region119 of a power FinFET structure can include a single vertical fin 111forming the device channel, whereas a logic device can include multiplefins 111 on the same bottom source/drain 118, in which case the logicdevices could lose the benefit of the inverted T-shaped conductiveregion. Compared to a VMOS FET with a V-shaped gate, the presentstructure is simpler and can be integrated into the vertical FinFETfabrication process flow. The power FinFET and logic devices can be madeat the same time using the same processes and layers.

In a non-limiting exemplary embodiments, current can flow from a topsource of the Power FinFET through the vertical fin channel to thelightly doped well 116 without a bottom source/drain region, across tothe electrical contact 250, and up the bottom electrical contact 260,which can be at 10 volts. A higher resistance of the lightly doped well116 can reduce the current through the channel compared to a highlydoped source/drain to avoid destroying the power device.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers can also be present.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Having described preferred embodiments of a device and fabricationmethod (which are intended to be illustrative and not limiting), it isnoted that modifications and variations can be made by persons skilledin the art in light of the above teachings. It is therefore to beunderstood that changes may be made in the particular embodimentsdisclosed which are within the scope of the invention as outlined by theappended claims. Having thus described aspects of the invention, withthe details and particularity required by the patent laws, what isclaimed and desired protected by Letters Patent is set forth in theappended claims.

What is claimed is:
 1. A method of forming a logic device and a powerdevice on a substrate, comprising: forming a first vertical fin on afirst region of the substrate and a second vertical fin on a secondregion of the substrate, wherein an isolation region separates the firstregion from the second region; forming a first doped well in thesubstrate under the first vertical fin on the first region and a seconddoped well in the substrate under the second vertical fin on the secondregion; forming a first bottom source/drain region in the first dopedwell under the first vertical fin on the first region, wherein a bottomsource/drain region is not formed in the second doped well under thesecond vertical fin, and forming a dielectric under-layer segment on thesecond vertical fin on the second region; forming a first gate structureon the dielectric under-layer segment and second vertical fin on thesecond region; and forming a top source/drain on each of the firstvertical fin and the second vertical fin, wherein the top source/drainon the second vertical fin is above the first gate structure.
 2. Themethod of claim 1, wherein the dielectric under-layer segment has athickness in a range of about 5 nm to about 10 nm.
 3. The method ofclaim 1, wherein the dielectric under-layer segment is made of amaterial selected from the group consisting of silicon oxide (SiO),silicon oxynitride (SiON), silicon boro carbonitride (SiBCN), siliconoxycarbonitride (SiOCN), and combinations thereof.
 4. The method ofclaim 1, wherein the first gate structure includes a gate dielectriclayer on the dielectric under-layer segment, a work function layer onthe gate dielectric layer, and a conductive gate fill on the workfunction layer.
 5. The method of claim 1, further comprising forming asecond gate structure on the first vertical fin on the first region,wherein the second gate structure includes a second gate dielectriclayer on the first vertical fin, a second work function layer on thegate dielectric layer, and a second conductive gate fill on the secondwork function layer.
 6. The method of claim 5, forming a bottom spacerlayer on the first region of the substrate and the second region of thesubstrate, wherein the second gate structure on the first vertical finon the first region includes a horizontal portion of the second gatedielectric layer in physical contact with the bottom spacer layer on thefirst region of the substrate, and the first gate structure on thesecond vertical fin on the second region includes a horizontal portionof the first gate dielectric layer in physical contact with thedielectric under-layer segment, and a conductive region on the secondregion has an inverted T-shape.
 7. The method of claim 1, wherein thefirst bottom source/drain region has a dopant concentration of at least5 times the dopant concentration of the first doped well.
 8. The methodof claim 1, further comprising forming a contact layer on the topsource/drains, the second doped well, and the first bottom source/drainregion.
 9. A method of forming a logic device and a power device on asubstrate, comprising: forming a first vertical fin on a first region ofthe substrate and a second vertical fin on a second region of thesubstrate, wherein an isolation region separates the first region fromthe second region; forming a first doped well in the substrate under thefirst vertical fin on the first region and a second doped well in thesubstrate under the second vertical fin on the second region; forming abottom source/drain region in the first doped well, wherein a bottomsource/drain region is not formed in the second doped well under thesecond vertical fin; forming a dielectric under-layer on the firstvertical fin and the second vertical fin; forming a masking block on thedielectric under-layer and second vertical fin on the second region thatleaves a portion of the dielectric under-layer on the first vertical finexposed; removing the exposed portion of the dielectric under-layer toform a dielectric under-layer segment on the second vertical fin;removing the masking block; forming a gate dielectric layer on thedielectric under-layer segment and first vertical fin on the firstregion; and forming a top source/drain on a top surface of each of thefirst vertical fin and the second vertical fin.
 10. The method of claim9, wherein the dielectric under-layer segment is made of a materialselected from the group consisting of silicon oxide (SiO), siliconoxynitride (SiON), silicon boro carbonitride (SiBCN), siliconoxycarbonitride (SiOCN), and combinations thereof.
 11. The method ofclaim 10, wherein the gate dielectric layer is made of a materialselected from the group consisting of silicon oxide (SiO), siliconnitride (SiN), silicon oxynitride (SiON), boron nitride (BN), high-kdielectric materials, and combinations thereof.
 12. The method of claim11, wherein the gate dielectric layer has a thickness in the range ofabout 7 Å to about 30 Å, and the dielectric under-layer segment has athickness in the range of about 5 nm to about 10 nm.
 13. The method ofclaim 12, further comprising forming a bottom spacer layer on thesubstrate below the gate dielectric layer and the dielectric under-layersegment.